(4) Precautions
1. The ratio of pigment to varnish can vary depending on the specific situation, and should not be the same. The resulting slurry satisfies the requirements. For example, when the ratio of carbon black and varnish is 1:4, it is more satisfactory, and so on. Schedule data for reference.
2. If the slurry is too thick or too thin, it can make the scratching unsatisfactory. Generally, the fluidity of the slurry is between 25-35 mm.
3. The number of grinding times in the schedule, for example, 3×50, means that after each 50 grindings, the toner is collected in the center of the frosted glass of the grinding apparatus with a doctor knife, and then the grinding is repeated. This is repeated three times. This equals a total of Research 150 times. 6 × 50, that is equal to a total of 300 grinding, and so on.
4. The sharpness of the scraper can also affect the quality of the scraping. If the squeegee is relatively blunt, the resulting scratched film is relatively thick, making comparison difficult. In this case, the angle of the squeegee can be increased during the squeegee so that the blade edge is perpendicular to the plane of the paper, so that the squeegee layer is ideal.
5. The quality of the paper can greatly affect the quality of the color comparison. Therefore, strict selection must be made. Yellow, rough surface, uneven internal structure of the paper are not applicable. Such as the use of senior securities paper, it is ideal.
Second, the density (specific gravity)
(I) Purpose and Definition
The density and specific gravity of objects are different in terms of physical concepts, but in practice, they are often confused.
Simply put, the ratio of the weight of an object to its volume is the proportion of it.
The specific gravity of organic pigments is generally between 1-2 g/cm3. The specific gravity of inorganic pigments is generally between 1.8 and 8.5 g/cm3. The proportion of carbon black is about 1.8 g/cm3.
The specific gravity of the pigment has a great influence on the quality of the ink. The pigments with larger specific gravity are generally less satisfactory, mainly due to poor transfer (transfer) properties in paste inks (such as glue and printing inks), and are easy to paste and plate; in liquid inks. (such as flexography, gravure ink) is mainly expressed as precipitation, agglomeration and so on.
There are also many methods for determining the specific gravity. The more accurate one is the method of replacing the air with vacuum with kerosene, but it is rather annoying.
Here is a simpler way to compare specific weights.
(B) Appliances and Materials
1. appliance
(1) 1/10000 balance.
(2) A specific weight cylinder with a capacity of 5 ml.
(3) Pipettes with a capacity of 5 ml.
2. material
(1) Kerosene (can be replaced with ink oil).
(c) Methods
Use a pipette to remove 4 milliliters of clean, uncontaminated kerosene, place it in a dry, uncontaminated volume, and carefully record the height of the liquid surface. Then pre-scaled pigment (0.4-0.5g of specific gravity, 1-1.5g of specific gravity, the pigment should be first dried at 105-110°C for 2 hours) carefully in the kerosene inside the measuring cylinder, Carefully record the height of the liquid surface, and calculate the following formula: d=w/ab. Where: d = specific gravity; W = amount of pigment; a = volume of pigment and kerosene; b = volume of kerosene.
(4) Precautions
1. The range of boiling range of kerosene is relatively large, in which the low-boiling part can be volatilized at room temperature, and it is easy to bring errors. Therefore, it is ideal to use high-boiling ink oil.
2. After the pigment is dried at 105-110°C, it should be placed in a drying tower and used after cooling.
3. When the kerosene is transferred into the measuring cylinder with a pipette, the amount of contamination of the kerosene should be avoided.
4. It is also not possible for the pigment to contaminate the cartridge wall.
5. Do not hold the cylinder containing kerosene for long periods of time in order to avoid inaccurate results due to volume expansion.